1. Field of the Invention
The present invention is in the field of hand tools and more specifically relates to a hand tool for holding a disc while the circumference of the disc is being ground to produce a disc having a desired diameter.
2. The Prior Art
One way of producing a disc of a desired diameter is as follows. A number of disc-shaped blanks are punched from a sheet or plate of the chosen material. These blanks do not have the desired final diameter due to the fact that a punch of the right size may not be commercially available, and due to the lack of precision inherent in the punching process. In addition, the punched blanks may have burrs or irregular edges. The tool of the present invention is used for holding a punched blank while the circumferential edge of the blank is ground, to bring it to the desired diameter and to eliminate the burrs and irregularities.
In U.S. Pat. No. 163,683 issued May 25, 1875 to Norton, there is shown a clamp for use in grinding watch crystals. The crystal is held between elastic-faced grippers each of which rotates about an axis that is perpendicular to a jaw of the clamp. The jaws open and close by pivoting about a pin.
In U.S. Pat. No. 2,551,648 issued May 8, 1951, to Suben, there is shown a tool for use in beveling a lens. As in Norton's tool, the jaws are connected by a pivot. Also, a spring is used to urge the jaws closed. Each jaw terminates in a rotating gripper.
The tools of Norton and of Suben are designed for working with discs of a particular thickness. Because the jaws are connected by a pivot, as the jaws are opened to accommodate a thicker disc, the axes of the rotating grippers cannot remain in a single straight line. The elastic facing of the grippers can accommodate only relatively small variations of disc thickness. Larger variations in disc thickness disrupt the gripping action and may cause the disc to become dislodged.
With this problem in mind, the present inventor set out to design a disc grinder capable of being used with discs having a wide range of thicknesses.